The lead up to the Brexit referendum was marked by widespread confidence that the UK would continue to remain in the EU. Complacency was epidemic, from strong market optimism (which would later suffer a heavy landing) to the unwillingness of businesses and politicians to consider the consequences of a change from the status quo – including, notably, prominent members of the Leave campaign.

March to protest against the result of referendum on British membership of the European Union. Photo by: Sam Greenhalgh. Source: Flickr Creative Commons.

This confidence persisted even when polling suggested a close race, with roughly equal proportions in favour of the UK remaining and leaving the EU. It is astounding, then, that political, business and civil society leaders – facing the odds of a coin toss – were so unprepared for the outcome that emerged in the early morning hours of 24 June.

One explanation for why so many were caught off-guard is the presence of groupthink, which occurs when a group’s ability to evaluate a situation and make sound decisions is impaired by the desire to maintain consensus and people’s willingness to obediently go along with the flow. Groupthink weakens the quality of decision-making by creating an echo chamber where opposing views and critique are dismissed, assumptions go unquestioned, decision biases and blind spots are enlarged, and where discussion revolves around conclusions in search of an argument rather than the rational appraisal of alternatives.

Notable examples of groupthink include the failure by governments and institutions to anticipate the global financial crisis, the US’s failure to anticipate the attack on Pearl Harbour, and the Bay of Pigs invasion. In all three instances, risks, warning signs and alternatives were ignored or censored by social pressure for unity.

Discussion and debates ahead of the referendum showed numerous symptoms of groupthink. Remain campaigners, for example, were overoptimistic in their belief that the economic case would ultimately triumph over other issues at stake. Many stereotyped Leave voters as “stupid”, “xenophobic” and “bigots”, thereby eliminating the need to engage meaningfully with their concerns about sovereignty and elevating the moral case for the Remain side. Remain supporters from across the board, including politicians, business leaders and commentators, were frequently overconfident in their predictions (relying on gut instincts instead of evidence) and closed-minded to opposing ideas.

Brexit is yet another example of how groups of intelligent and competent individuals can be blindsided. Referendum predictions in favour of Remain were often detached from reality, and there was widespread failure to assess the risks and consequences of a wrong prediction. The lack of preparation is even more striking given that the potential losses from the UK leaving the EU significantly outweighs potential gains from preserving the status quo.

In light of these dangers, what can decision-makers do to protect themselves from groupthink?

First, it is crucial to have diversity at the decision-making table. Diversity enables a broader range of perspectives and experiences to be shared and drawn from, and ultimately leads to richer discussions and insights. In the case of Brexit, many of the echo chambers were created by groups of people with similar attitudes, values, or backgrounds, creating blind spots and tunnel vision.

Secondly, the culture and norms that influence meetings should encourage constructive dissent and allow for different perspectives to be expressed and considered. Groups should ensure that they do not belittle opposing views and positions by cherry-picking weak or straw man arguments, but give due weight and consideration to dissenting opinions and concerns.

Finally, these norms must be championed and fostered by leaders and chairs committed to facilitating productive meeting environments, vigilant against the symptoms of groupthink, and active in assessing and managing risk. Creating the right balance between encouraging diverse perspectives and disagreement on the one hand with maintaining group chemistry and consensus on the other is no small feat.

We need governments and institutions to deliver strong and effective leadership, by being open to alternative viewpoints so that they can think critically and creatively about complex issues. Brexit’s echo chambers are a timely reminder for decision-makers to take their blinkers off and to be alert to the perils of groupthink.

Alice Wang is studying for an MPP at the Blavatnik School of Government and is currently researching diversity, groupthink and effective decision-making for her summer project. Alice can be found on Twitter at @helloalicewang.